Background: Sexual minority adolescents appear to be at increased risk for internalizing disorders relative to their heterosexual peers, but there is a paucity of research explaining this elevated risk. Emotion regulation deficits are increasingly understood as important predictors of internalizing psychopathology among general samples of adolescents. The present study sought to examine whether deficits in emotion regulation could account for disparities in internalizing symptoms between sexual minority and heterosexual adolescents. Methods: The present study utilized longitudinal data from a racially/ethnically diverse (68% non-Hispanic Black and Hispanic/Latino) community sample of 1,071 middle school students (ages 11-14). Results: Adolescents who endorsed same-sex attraction evidenced higher rates of internalizing symptoms at both time points. Structural equation modeling indicated that sexual minority adolescents exhibited greater deficits in emotion regulation (rumination and poor emotional awareness) than their heterosexual peers. Emotion regulation deficits in turn mediated the relationship between sexual minority status and symptoms of depression and anxiety. Conclusions: The results demonstrate the importance of considering normative psychological processes in the development of internalizing symptomatology among sexual minority adolescents, and suggest emotion regulation deficits as specific targets of prevention and intervention efforts with this population. Future studies are needed to determine whether stigma-related stressors are responsible for emotion regulation deficits among sexual minority youth.